Power transmission



Filed July 10, 1952 R 0 T A E V I ADOLF KEEL.

ATTORNEY United States Patent '0 POWER TRANSMISSION Adolf Keel, HighlandPark, Mich, assignor to Vickers Incorporated, Detroit, Mich., acorporation of Michigan Application July 10, 1952, Serial No. 298,077

1 Claim. (Cl. 103-162) This invention relates to power transmissions,and is particularly applicable to those of the type comprising two ormore fluid pressure energy translating devices, one of which mayfunction as a pump and another as a fluid motor.

The invention is more particularly concerned with a fluid pump or motorconstruction of the type having a rotary cylinder barrel abutting astationary valve plate, and provided with axial cylinders'and pistonsreciprocable therein which abut against a thrust plate, the axis ofwhich is inclined to the axis of rotation of the cylinder barrel. It isparticularly concerned with that class of devices wherein the pistonsabut directly against the inclined thrust plate without the use ofarticulated connecting rods so that the driving torque is transmittedthrough the pistons acting as centilevers by reason of that component ofpiston thrust against the inclined thrust plate which is normal to theshaft axis.

In such devices, the normal thrust component, or side thrust on thepiston, not only creates the driving torque but also results in asubstantial lateral force on the cylinder barrel tending to displace itfrom its normal position. In counteracting this lateral force it isimportant that the cylinder barrel be maintained flatly against thevalve plate or it will frequently lift off completely due to fluid flowconditions set up when it starts to lift slightly. This of courserenders the whole device inoperative and may be very hazardous where thedevice is connected to operate certain types of loads. The axial.location of the point of application of the cylinder barrel supportingforce may be so selected as to minimize tilting forces on the barrel aslater described.

In prior art devices of this class, support for the cylinder barrelagainst lateral displacement has been provided by two general schemes.The first of these provides a radial bearing encircling the cylinderbarrel directly interposed between the cylinder barrel and the housing.The second scheme has been to support the cylinder barrel directly onthe shaft at the driving connection therewith and transmit the lateralthrust thereon to the housing through the shaft and shaft support. Theadvantage of the first scheme lies in the fact that the cylinder barrelsupport bearing may be axially positioned so to eliminate tiltingmoments on the barrel produced by the side thrust applied to thecantilever pistons. Disadvanatges of the first scheme are that a largebearing encircling the cylinder barrel increases the size and weight ofthe unit, and of course requirement of an extra bearing increases cost.Advantages of the second scheme include the fact that the shaft bearingsserve a double purpose in supporting the shaft and the cylinder barrel,thus reducing size, weight, and cost of the unit. Disadvantages of thesecond scheme are that the heavy radial loads on the shaft of highpressure units have in the past required that the shaft bearingsstraddle the point of cylinder barrel support to provide adequate support for the shaft. Such an arrangement results in in- Patented Jan. 5,i957 ice creased machining costs and is unsatisfactory for otherreasons.

It is an object of the present invention to provide a construction whichhas the advantages of both the schemes heretofore mentioned but is freefrom their disadvantages.

More specifically, it is an object of the present invention to provide adevice of the class described wherein the cylinder barrel is drive shaftsupported but the moment on the shaft caused by the cylinder barrel isso reduced as to eliminate the necessity for shaft supports straddlingthe point of cylinder barrel support.

Another object is to provide such a device which is rugged, compact, andeconomical to manufacture.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing wherein a preferred form of the present invention is clearlyshown.

In the drawing the single figure is a longitudinal transverse section ofa fluid pressure energy translating device incorporating a preferredform of the present invention.

The embodiment of the invention selected for illustration comprises apump 10 of the cantilever piston type. The housing 12 of pump 10comprises two parts 14 and 16 secured together by bolts 18. An 0 ringseal 20 insures a fluid tight juncture of the two parts and the dowelpin 22 maintains proper angular alignment between them. Body 12 includesa pilot portion 24 and a mounting flange 26 having mounting holes 28therein.

A bore 36 in housing 12 provides a chamber 32 having a cylinder barrel34 positioned therein. Cylinder barrel 34 is provided with a pluralityof bores 36 each having a piston 38 axially slidable therein and acylinder port 37. Pistons 38 have spherical ends 40 on which are swagedthe socketed shoes 42. The cylinder barrel 34 is positioned axiallybetween a valve plate 44 and an inclined thrust plate 46. Valve plate 44may be the type described in the patent to Harry F. Vickers et al.,2,313,407, and serves in a well known manner to provide properly phasedfluid connection between ports 37 ofbores 36 and the external inlet andoutlet connection ports of the device, one of which is indicated at 48.Thrust plate 46 is secured to the housing 12 by a number of screws 50sealed against leakage from chamber 32 by 0 rings 52.

Shoes 42 have outwardly extending flanges 54 which are contacted by anannular cage 56 provided with holes 58 corresponding to each piston 38.A sleeve 60 is provided with a shoulder 62 to contact cage 56 and has atruncated conical bore 64 therein. Conical bore 64 contacts thespherical outer surface 66 of a collar 68 which is provided with afemale spline to engage a male spline in the cylinder barrel at 70. Aplurality of springs 72 in recesses 74 in cylinder barrel 34 act throughcollar 68, slevee 6%, and cage 56 to bias the shoes 42 into engagementwith the face 47 of thrust plate 46. The reaction force of springs 72biases face 35 of the cylinder barrel 34 into engagement with face 45 ofvalve plate 44.

A drive shaft 76 is effective to transmit torque from a prime mover, notshown, to the cylinder barrel through a driving connection at 78.Further, it can be seen that the only radial support for cylinder barrel34 is provided by the contact between the barrel and the shaft 76 atconnection 78. Connection 78 is illustrated as a spline connection andpreferably is of the universal type, that is, it prevents relativeradial movement at the point of connection between shaft 76 and barrel34 but permits axial movement of the barrel and existence of angularitybetween the shaft and cylinder barrel axes. Thus juncture of the faces35 and 45 locates cylinder barrel 34 as to axial position and determinesthe angular position of its axis, and connection 78 locates the barrelradially.

Neglecting friction, torque applied to cylinder barrel by drive shaft 76is resisted by a force exerted on shoes 42 and hence pistons 38 bythrust plate 46. The force on each piston acts in a t'irection normal toface 47 of thrust plate 46 and has an effective point of application atthe center of the spherical ends 40 of the pistons 30. This force oneach piston can be resolved into an axial force and a radial forceacting at the center of the spherical piston end. The summation of theradial forces is the radial force which must be supported by shaft 76 atthe connection 78.

It is well known in the art that tipping forces on the cylinder barrelof such a unit can be kept to a minimum by providing its radial supportas close as possible to a radial plane through the point of intersectionof the drive shaft axis and the plane which includes the centers of thespherical ends of the pistons. The plane containing the centers of thepiston ends is indicated at 80 and the point of intersection with theshaft axis at 82. It can be seen that connection 78 is axially centeredabout the intersection 32 thus minimizing tipping forces on the barrel34.

One of the undesirable consequences of thus positioning connection 78 isthat, prior to the present invention, the heavy radial loads exerted onthe drive shaft at connection 78 created very large bending moments onthe shaft if it was cantilever supported by bearings all on the sameside of the connection. For high pressure units it became necessary toprovide shaft support on each side of the shaft and cylinder barrelconnection resulting in more expensive construction and presentingparticular difiiculty if the unit was to be a variable delivery one.

The present invention provides a cylindrical support sleeve 84, on theportion 14 of housing 12, which protrudes from the face 86 against whichface the valve plate 44 rests. Sleeve 84 has a bearing bore 88 at itsoutward end and carries a shaft support bearing 90 therein. A secondshaft support bearing 92 and a shaft seal 94 are provided in the shaftbore 96. Valve plate 44 and cylinder barrel 34 are provided withclearance bores 98 and 100, respectively, through which sleeve 84passes. Bearing 90 is thus positioned in axial proximity to theconnection 78 and the bending moment created by the radial load ofbarrel 34 on shaft 76 is minimized.

It will thus be seen that the present invention provides support on thedrive shaft for the cylinder barrel to resist lateral movement and thatsupport is properly positioned to minimize tilting of the barrel.Further, the

invention provides tor supporting the drive shaft in such a manner as tominimize bending moments produced thereon by lateral thrust of thecylinder barrel. This of course results in lowered stresses anddeflections in the drive shaft making feasible the rugged economicalconstruction illustrated.

While the form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claim whichfollows.

What is claimed is as follows:

A fluid pressure energy translating device comprising: a drive shaft; ahousing having a stationary valve plate; a rotatable cylinder barrel inabutment with the valve plate and in driving relation with the driveshaft and having a plurality of axial cylinder bores; pistonsreciprocable in the bores, each having a cantilever portion extendingfrom the bores and having a spherical surface at one end of each piston;an inclined thrust plate mounted in the housing in driving relation withthe pistons at their spherical ends; inlet and outlet ports alternatelyconnectable through the valve plate to said cylinder bores by rotationof the cylinder barrel; means on the shaft for locating the barrel as tolateral position, and forming the sole lateral support therefor, saidmeans including in its axial extent the point on the shaft axis whichintersects the plane containing the centers of said spherical surfaces;means in said housing for rotatably supporting the drive shaft, saidmeans including a support sleeve in the housing encircling the driveshaft and extending axially along the drive shaft from the juncturebetween the valve plate and the cylinder barrel toward said means on theshaft, and bearing means carried by said sleeve to contact said shaft;and a cantilever projection of said shaft extending beyond said bearingmeans and including said means on the shaft.

References Cited in the file of this patent UNITED STATES PATENTS1,263,180 Williams Apr. 16, 1918 1,822,064 Sorensen Sept. 8, 19312,480,069 Wright Aug. 23, 1949 2,546,583 Born Mar. 27, 1951 2,642,810Robinson June 23, 1953 FOREIGN PATENTS 500,299 Great Britain Feb. 7,1939 937,497 France 1948

